Underdogs and the moral high ground of victims

Research on 'underdogs'; that is the attitudes to those perceived as such shows that

No matter what scenario the participants were presented with, they consistently favored the underdog to win.

The research doesn't tell us why but; "The researchers propose that those who are viewed as disadvantaged arouse people's sense of fairness and justice -- important principles to most people."
which is probably true, but the implications are possibly greater if my hypothesis that the underdog thing is linked to the victim thing which then becomes a rhetorical device to win arguments if only one can frame ones interest as an underdog or victim. At one level it is hopeful that there is this bias to the underdog on the other hand it probably means that there really is a rhetorical leverage. And perhaps one of the interesting things about the Israel-Palestine situation is that the victim/underdog card is being played by both sides in different ways.

A further interesting question is why this 'bias to the underdog' doesn't translate into more just and fair global institutions. Is it that the underdog thing only really operates with observing third parties?
Why Do People Support Underdogs And Find Them So Appealing?: